Answer:
I'm assuming you mean in an academical debate.
Explanation:
-Have a thesis (argument) that you can back up strongly, and with facts.
-Prepare counterarguments. Think about what your opponent might say. And think about what you would respond to that.
But if you mean just any argument, just state what you think and why. If they don't believe you, either you are wrong, they are stubborn, or its an opinion lol